The UCSD CD4 Collaborative Clinical Trials Unit (CTU) will bring together six dynamic and diverse Clinical Research Sites (CRSs) that are well prepared to respond to the research priorities of the NIAID HIV/AIDS clinical research networks. Our CTU brings together the scientific expertise and experience required to conduct a broad variety of complex clinical trials in adults, adolescents, children and pregnant women in the areas of HIV therapeutic interventions aimed at cure, functional cure and eradication of HIV; new and novel antiretroviral drug development; HIV-related co-infections and comorbidities, including opportunistic infections and other end organ diseases; treatment and prevention of tuberculosis (TB) in HIV co-infected and TB mono-infected individuals; treatment and cure of viral hepatitis in co-infected and mono-infected individuals; biomedical and behavioral interventions to reduce or prevent HIV transmission (including pre-exposure prophylaxis, post-exposure prophylaxis and vaccine prevention strategies) in high risk populations, including pregnant women; and in the pathogenesis of HIV disease, including viral persistence, latent reservoirs, viral and vaccine immunology, and vaccine development. Through our CD4 Collaborative CTU we will address the following specific aims (briefly summarized here): Specific Aim 1 (Innovative Science Infrastructure): Provide scientific expertise and efficient, flexible infrastructure to develop new strategies to improve the prevention and treatment of HIV infection within the context of the following NIAID Clinical Research Networks on: a) Therapeutics for HIV/AIDS and HIV associated Infections in Adults; b) HIV/AIDS and HIV-associated Infections in Pediatric and Maternal Populations; c) Integrated Strategies to Prevent HIV Infection; d) Vaccines to Prevent HIV Infection. Specific Aim 2 (Effective Scientific Leadership): Provide excellent, effective leadership in administrative coordination and scientific participation within the CTU, across the CRSs, within communities served by the CTU, and across the clinical research networks in which our CTU will participate. Specific Aim 3 (Effective Fiscal Management and Performance): Effectively manage all financial and infrastructure resources, and oversee, evaluate and assure exemplary performance of all components. Specific Aim 4 (Community Engagement): Engage and partner with affected communities to shape network scientific agendas and to recruit, enroll and retain ideal research trial participant in network studies.